Propeller



March 15, 1938. E. DROULLARD 2,111,093

PROPELLER Filed 001;. 7, 1935 15 INVENTOR 5014/??? DROUZLHED ATTORNEY.

Patented Mar. 15, 1938 UNITED STATES PROPELLER Edward Droullard,Detroit, Mich. Application October 7, 1935, Serial No. 44,073

3 Claims.

The present invention pertains to a novel propeller used in connectionwith a boat, although the invention is not limited to any particularform of boat in combination with the propeller.

The object of the invention is to provide a propeller of higher thanusual efliciency.

In connection with this object, I have observed that the leading edge ofmost propeller blades of the prior art lies perpendicular to the axis ofthe shaft, regardless of the slope of the body of the blade. In thepresent invention, the leading edge of the blade lies at the desiredpitch angle to the axis of the shaft, the body of the blade beingsubstantially in a plane with the leading edge, the blade being withoutthe usual twist although scooped slightly at its rear face and concaveslightly at its forward face for better action in the water.

Further the conventional propeller blade lies entirely within a quartercircle around the propeller shaft. In the present invention, the bladelies in two quadrants around the propeller shaft axis, presenting aleading edge prolonged across the axis of the shaft in a substantiallystraight 5 line at a pitch angle to the axis.

The invention is fully disclosed by way of example in the followingdescription and in the accompanying drawing in which Figure l is a sideelevation of a boat and pro- 30 pellers according to the invention;

Figure 2 is an end view;

Figure 3 is an elevation of the propeller blade, viewed perpendicularlyto the face of the blade;

Figure 4 is a plan view of the blade, and

35 Figure 5 is a section on the line 5-5 of Figure 4.

Reference to these views will now be made by use of like characterswhich are employed to designate corresponding parts throughout.

In Figure 1 is shown a motor boat or speed boat 40 I of more or lessconventional design except for certain particulars to be describedbelow. From a point 2 approximately directly below the drivers station,the keel 3 is arched or concaved upwardly as indicated by the numeral 4,to the 45 stern. A hearing 5 is mounted in the keel at the point 2, anda combined bearing and gear casing 6 is supported in the arch near thestern. In these bearings is journaled a propeller shaft 1 with itsforward end approximately two inches 50 higher than its rear end. Anintermediate bearing 8 for the shaft is provided if necessary.

In the boat is provided an engine 9 with a drive shaft Ill geared at l lto the shaft 1 at a ratio of two to one. In the stem is mounted theusual rudder l2.

Since the propeller blades are mounted at intervals on the shaft 7, eachis preferably formed as an integral part of a hub I3. The blade propermay best be described with relation to its leading edge 14 as seen intop plan in Figure 4. This edge 5 lies at one side of the axis of thehub for the propeller shaft, in a straight line at a fixed angle to thisaxis. Also, this edge is prolonged slightly at the other side of theaxis as indicated by the numeral l5, so that the leading edge may besaid 10 to be a substantially straight line prolonged across thepropeller shaft axis at a fixed angle. From the outer end of the line15, the trailing edge of the blade follows a downward curve on agradually increasing radius, to a point directly below 15 the hub axis.This curve is indicated by the numeral It. From the last named point,the trailing edge of the blade slopes in a nearly straight line I! tothe outer end of the line [4 but is rounded at its lower end to mergewith the 20 line l6 and also at its upper end to avoid a sharp corner inmeeting the line I4. I

The blade lies substantially in a plane with the line H! asdistinguished from the twist in the usual propeller blade to provide theproper pitch angle beyond the shank or neck of different angle lyingimmediately adjacent to the hub. However, the blade is slightly dishedto form a convex forward face and a concave rear face l8 for a scoopingaction in the water.

The distances from the axis to the bottom of curve I6 and to the outerend of line 14 are approximately equal. By reason of the leading edgebeing prolonged across the propeller shaft axis as previously set forth,there is provided a comparatively long cutting edge with relation to theextent of projection of the blade outwardly from the shaft, so that thelength of cutting edge within a given turning radius is considerablyincreased. The prolongation of the leading edge across the shaft axisdistributes the weight of the blade in two quadrants around the axis oron both sides of a plane passing through the axis and perpendicular tothe edge I l, l5. Such construction is better balanced and more durablethan in the usual case where the blade lies entirely in one quadrantaround the propeller shaft axis. Although the edge I4 is longer than theedge 15, the weight of the blade is substantially equal on both sides ofa normal to said edges, because of the tapering of the blade along linell and the thinning of the metal towards the outer ends of lines l4, H.

In connection with the arched bottom, it is well known that at highspeed a propeller has a tendency to sink into the water. A boat having asingle propeller at the stern lifts its bow out of the water at highspeed. The long propeller here disclosed would pull the boat into thewater to an undesirable depth. This tendency is overcome in the presentinvention by the arched bottom which receives an increasing upward forcefrom the Water at high speed. In other words, the arched bottom wedgesthe boat upwardly, thereby balancing to some extent the downward pull ofthe propeller at high speed. The water lines when standing and at highspeed are indicated by the numerals l9 and 20 respectively, and the boatis always level due to the substantial length of the arch 4.

The shaft, preferably tapers from stern to bow so that the rearwardforce on the propellers tightens the hubs IS on the shaft. Each hub iskeyedv to the shaft as indicated by the numeral 2! in.

Figure 5.

Although a specific embodiment of the invention hasbeen illustrated anddescribed, it will be understood that various alterations in the detailsof construction may be made without departing from the scope of theinvention, as indicated by the appended claims.

What I claim is:

1. A propeller comprising a hub, a blade mounted thereon presenting astraight leading edge at an oblique angle to said hub and prolongedacross said hub, said blade having a convex rear edge extending from theouter end of said leading edge to the outer end of its prolongation,said leading edge'being substantially longer than its prolongation, theradius of curvature of said rear edge increasing from said prolongationto its intersection with a normal to the hub end of said leading edge,said rear edge sloping from said intersection to the free end of saidleading edge, and the weight of said blade being substantially equal onboth sides of said normal.

2. A propeller comprising a hub, a blade mounted thereon presenting astraight leading edge at an oblique angle to said hub and prolongedacross said hub, said blade having a convex rear edge extending from theouter end of said leading edge to the outer end of its prolongation,said leading edge being substantially longer than its prolongation, thedistance from said axis to said convex edge on the line perpendicular tosaid leading edge being substantially equal to the distance, from saidaxis to the forward end of said leading edge, the weight of .said bladebeing substantially equal on both sides of said line.

3. A propeller comprising a hub, a blade mounted thereon presenting astraight leading edge at an oblique angle to said hub and prolongedacross said hub, said blade having a convex rear edge extending from theouter end of saidleading edge to the outer endof. its prolongation, saidleading edge being substantially longer than its prolongation, saidblade having its forward face dished, said leading edge beingsubstantially longer than its prolongation, the radius of curvature ofsaid rearedge increasing from said prolongation to its intersection witha.- normal to the hub end of. said leading edge, said rear edge slopingfrom said .in tersection to the free. end of said leading edge, and theweight of said blade being substantially equal onboth sides of saidnormal.

EDWARD DROULLARD.

